EP1916123A1

EP1916123A1 - Tire with central rubber layer reinforced with micro and/or macro reinforcing fillers to abridge split carcass ply ends

Info

Publication number: EP1916123A1
Application number: EP07118988A
Authority: EP
Inventors: Paul Harry Sandstrom; Ping Zhang; Joseph Kevin Hubbell; James Joseph Golden; Robert Anthony Neubauer; Keith Carl Trares
Original assignee: Goodyear Tire and Rubber Co
Current assignee: Goodyear Tire and Rubber Co
Priority date: 2006-10-24
Filing date: 2007-10-22
Publication date: 2008-04-30
Also published as: US7631676B2; BRPI0703725A; CN101168340A; CN101168340B; US20080093003A1

Abstract

The invention relates to a tire (1) having a split carcass ply with the ends (4A, 5A) of the split carcass ply being spaced apart in a central crown portion of the tire and a central rubber layer (7A, 7B) spanning the gap (6) between the split carcass ply ends (4A, 5A), wherein said central rubber layer (7A, 7B) is reinforced with at least one of a micro and a macro reinforcing filler. Said central rubber layer (7A, 7B) may additionally contain continuous cord reinforcement.

Description

Field of the Invention

The invention relates to a tire having a split carcass ply with the ends of the split carcass ply being spaced apart in the crown portion of the tire and a central rubber layer spanning the gap between the split carcass ply ends, wherein said central rubber layer is reinforced with at least one of micro and macro reinforcing fillers. Said central rubber layer may additionally contain continuous cord reinforcement.

Background and Summary of the Invention

Pneumatic rubber tires are typically composed of a carcass of a ply construction where the carcass plies are composed of a rubber composition reinforced with continuous cords. Such cords may be composed of, for example, synthetic and/or natural filaments such as for example nylon, aramid, polyester and/or rayon filaments or may be composed of steel or coated steel filaments. Such rubber composition conventionally also contains a dispersion of reinforcing filler composed of particulate rubber reinforcing carbon black or a combination of rubber reinforcing carbon black and precipitated silica. The tire carcass conventionally supports a circumferential rubber tread which also contains a circumferential belt ply between the tire carcass and tread composed of, for example, a continuous cord reinforcement composed of, for example, a filamentary steel cord.
Tires having a carcass composed of split carcass plies have been proposed to provide a reduction on tire weight and cost. In this context, see US-B-7,017,635 and particularly its Figures 7 and 9 showing a tire carcass composed of cord reinforced split plies with a central ply spanning the gap between the split plies to abridge and join the split ply ends.
For this invention, it is proposed to provide a tire with cord-reinforced split radial plies having their split ply ends abridged and joined by at least one circumferential central rubber layer which abridges (and thereby joins) the split ply ends by overlapping and/or underlapping the split ply ends. The central rubber layer contains a dispersion of macro and/or micro reinforcement. Optionally, said central rubber layer may also contain continuous cord reinforcement.
A significant aspect of such abridging rubber layer, which spans the gap between the split carcass ends, is considered herein to be the inclusion of macro and micro reinforcement in its rubber composition. This is considered herein to be significant in a sense of simplifying the tire manufacturing process through the elimination of the calendering procedure for the preparation of rubber coated ply cords.
A further significant aspect of such abridging rubber layer, which spans the gap between the split carcass ends, is considered herein to be an optional additional inclusion of continuous cord reinforcement in its rubber composition. This is considered herein to be significant in a sense of further enhancing the reinforcing characteristics of the center ply, hence enhancing the performance of the tire.
The split ply tire carcass comprises at least two cord reinforced carcass plies having their ply ends spaced apart in the crown portion (central portion) of the tire carcass. The said carcass ply ends are joined by at least one central rubber layer which abridges and overlaps and/or underlaps the said carcass ply ends.
For example, the central rubber layer abridges the gap between the split carcass ends by being positioned radially outward from, and thereby overlapping and joining the carcass split ply ends.
For a further example, the central rubber layer abridges (spans) the gap between the split carcass ends by being positioned radially inwardly from, and thereby underlapping and joining, the carcass split ply ends.
For an additional example, the two central rubber layers, namely a first and second central rubber layer, abridge the gap between the split carcass ends wherein the first central rubber layer is positioned radially outward from, and thereby overlapping and joining, the carcass split ply ends and the second central rubber layer is positioned radially inward from, and thereby underlapping and joining, the carcass split ply ends. Optionally said first and second central rubber layers are in contact with each other to form a unitized configuration within the gap between the split carcass ends.
The central rubber layer composition comprises a rubber composition which contains a dispersion of macro and/or micro reinforcing fillers either to the exclusion of internal continuous cord reinforcement or in combination with internal continuous cord reinforcement.
Such macro reinforcement, for example, comprises short synthetic and/or natural filaments including cords comprising a plurality of such filaments. Representative of such synthetic and/or natural filaments are, for example, nylon, aramid, polyester, glass, steel, coated steel and/or rayon filaments.
Such micro reinforcement, for example, comprises at least one polymer selected from syndiotactic polybutadiene, and a poly alpha-olefin such as for example, ultra high molecular weight polyethylene (UHMWPE), polypropylene, polybutene and poly 4-methyl-1-pentene, in addition to at least one of particulate rubber reinforcing carbon black and synthetic amorphous precipitated silica.
A significant aspect of such abridging (spanning the gap between the split carcass ply ends) central rubber layer is considered herein as providing support to the gap between the split carcass ply ends in a sense of promoting supportive durability to the split carcass ply (e.g. promoting a continuation of the carcass ply across the gap between its split ply ends) and, further to promote additional strength for the gap between the carcass split ply ends with an inclusion of continuous cord reinforcement within the macro and/or micro reinforced central rubber layer.
In the description of this invention, the terms "rubber" and "elastomer" where used herein, are used interchangeably, unless otherwise prescribed. The terms "rubber composition", "compounded rubber" and "rubber compound", where used herein, are used interchangeably to refer to "rubber which has been blended or mixed with various ingredients" and the term "compound" relates to a "rubber composition" unless otherwise indicated.
In the description of this invention, the term "phr" refers to parts of a respective material per 100 parts by weight of rubber, or elastomer. The terms "cure" and "vulcanize" are used interchangeably unless otherwise indicated.
The term "melting point", or "MP", of a polymer refers to a melting point of a polymer determined by DSC (differential scanning calorimeter) at a heating rate of 10°C per minute, an analytical procedure well known to those having skill in such art.

Practice of the Invention

In accordance with this invention, a tire according to claim 1 is provided.
Preferably, the rubber composition of said abridging rubber layer contains from 1 to 30, alternately from 2 to 25, phr of said at least one of said macro and said additional micro reinforcing fillers such as, for example, from zero to 30, alternately from 1 to 25, phr of said macro reinforcing filler dispersion and from zero to 30, alternately from 1 to 25, phr of said additional micro reinforcing filler, based upon parts by weight per 100 parts by weight of the rubber (phr) of said rubber composition.
In practice, said short fibers for said macro reinforcing filler may be selected from natural and/or synthetic fibers such as, for example, at least one of nylon, polyester, rayon, aramid, cellulose and cotton. Said short fibers may preferably be comprised of at least one of nylon, cellulose, polyester and aramid.
In practice, said short fibers for said macro reinforcing filler preferably have an average length in a range of from 1.3 mm to 25 mm, alternately from 2.5 mm to 13 mm.
Said short fibers may be, for example, in a form of a chopped cord of a plurality of fibers (e.g. a cord of a plurality of fibers which has been chopped into short lengths).
Rubber reinforcing carbon black and/or precipitated silica filler is used in an amount ranging from 30 to 100 phr for the rubber composition of the central rubber layer.
In practice, a circumferential cord reinforced rubber belt ply is positioned radially outward of said split carcass ply elements and said abridging central rubber layer and between said split carcass ply elements and said circumferential rubber tread.
In practice the rubber composition of said abridging central rubber layer comprises at least one diene-based elastomer selected from polymers and copolymers of isoprene and 1,3-butadiene and copolymers of styrene and at least one of isoprene and 1,3-butadiene.
Representative elastomers for the rubber composition of said central rubber layer are, for example, styrene-butadiene copolymers (whether prepared by organic solvent solution polymerization or by aqueous emulsion polymerization), isoprene/butadiene copolymers, styrene/isoprene/butadiene terpolymers and tin coupled organic solution polymerization prepared styrene/butadiene copolymers, cis 1,4-polyisoprene and cis 1,4-polybutadiene.
Preferred elastomers are natural cis 1,4-polyisoprene rubber, styrene/butadiene rubber and cis 1,4-polybutadiene rubber.
Representative rubber reinforcing carbon blacks for the rubber composition of said central rubber layer may be referred to by their ASTM designations such as for example for tread rubber compositions, N110, N121 and N234. Other rubber reinforcing carbon blacks may found, for example, in The Vanderbilt Rubber Handbook (1978), Page 417.

Brief Description of the Drawings

FIG 1, FIG 2 and FIG 3 are provided to further illustrate the invention as a cross-section of a portion of a tire showing a tread with a belt ply underlying the tread and a cord reinforced split carcass ply underlying the belt ply composed of two split carcass ply elements having their split ply ends spaced apart in the central crown portion of the tire with an associated central rubber layer spanning the gap between the ends of the split carcass ply elements and overlapping, to thereby join, the split carcass ply ends and associated elements
FIG 4 and FIG 5 are provided to depict the central rubber layer.

Detailed Description

In FIG 1, FIG 2 and FIG 3, a simplified cross-section of a portion of a pneumatic tire 1 is shown with a circumferential tread 2 and an underlying carcass 3, identified in only a general way by an arrow in the drawing, together with a continuous cord reinforced split carcass ply composed of two continuous cord reinforced split carcass ply elements 4 and 5 with their split carcass ply ends 4A and 5A spaced apart from each other in the central crown portion of the tire with a resulting gap 6 between said split carcass ply ends 4A and 5A, at least one central rubber layer overlay 7A or underlay 7B and a circumferential continuous cord reinforced belt ply 8 underlying said tread 2, (and positioned radially outward of said split carcass ply elements in the crown portion of the tire).

FIG 1 depicts said tire 1 with a central rubber layer overlay 7A which spans the gap 6 between the split carcass ply ends 4A and 5A and overlaps the radially outer surfaces of split carcass ply elements 4 and 5 and split carcass ply ends 4A and 5A.
FIG 2 depicts said tire 1 with a central rubber layer underlay 7B which spans the gap 6 between the split carcass ply ends 4A and 5A and underlaps the radially inner surfaces of split carcass ply elements 4 and 5 and split carcass ply ends 4A and 5A.
FIG 3 depicts said tire 1 with a first central rubber layer overlay 7A and second central rubber layer underlay 7B, respectively, which, both span the gap 6 between the split carcass ply ends 4A and 5A, respectively, and;

central rubber layer

carcass ply elements

carcass ply ends

central rubber layer

carcass ply elements

carcass ply ends

In FIG 4 and FIG 5, central rubber layer(s) 7 is depicted.
In particular, FIG 4 depicts a first central rubber layer variation 7 which contains a uniform dispersion of a combination of macro reinforcing filler and said micro reinforcing filler, exclusive of continuous cord reinforcement.
In particular, FIG 5 depicts a second central rubber layer variation 7 which contains a uniform dispersion of a combination of macro reinforcing filler and said micro reinforcing filler together with continuous cord reinforcement 9.
The preparation of a tire carcass ply, including said split carcass plies, may be accomplished by conventional means such as, for example, by calendering procedures which are well known to those having skill in such art or by other procedures as may be appropriate.
It is readily understood by those having skill in the pertinent art that the rubber composition for the various tire components, including said split carcass plies and abridging rubber layer which spans the gap between said split carcass ply ends, would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials, as herein before discussed, such as, for example, curing aids such as sulfur, activators, retarders and accelerators, processing additives, such as rubber processing oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, microcrystalline waxes, antioxidants and antiozonants, peptizing agents and reinforcing materials such as, for example, carbon black. As known to those skilled in the art, depending on the intended use of the sulfur vulcanizable and sulfur vulcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.
The vulcanization is preferably conducted in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents may include, for example, elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur. As known to those skilled in the art, sulfur vulcanizing agents might be used in an amount ranging from, for example, 0.5 to 4 phr. Vulcanization accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. Sometimes a single accelerator system is used, i.e., a primary accelerator. More typically, various combinations of primary and secondary accelerators are used with the secondary accelerator being used in smaller amounts (of 0.05 to 3 phr) in order to activate and to improve the properties of the vulcanizate. In addition, delayed action accelerators may be used which are not particularly affected by normal processing temperatures but produce a more satisfactory cure at higher vulcanization temperatures. Vulcanization retarders might also be used. Suitable types of accelerators that may be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. The primary accelerator may often be a sulfenamide. If a second accelerator is used, the secondary accelerator is usually preferably a guanidine, dithiocarbamate or thiuram compound.
The mixing of the rubber composition can be accomplished by a sequential mixing process comprised of at least one non-productive mixing step followed by a productive mixing step. For example, the ingredients may be mixed in two or more (sometimes at least three mixing stages), namely, at least one non-productive (preparatory) stage followed by a productive (final) mix stage. The final curatives are typically mixed in the final stage which is conventionally called the "productive" or "final" mix stage in which the mixing typically occurs at a temperature, or ultimate temperature, lower than the mix temperature(s) of the preceding non-productive mix stage(s).
The following Examples are presented to further illustrate the invention. The parts and percentages are by weight unless otherwise indicated.

Example I

Rubber samples of rubber compositions which contain a micro reinforcement for use for an abridging rubber layer for the split ply tire carcass of this invention (to span the gap between split carcass ply ends in the crown portion of the tire) is prepared and identified herein as Control Sample A and experimental Samples B and C which contain UHMWPE, i.e. polyethylene having a molecular weight of more than 500000 mol/g, preferably more that 2,000,000 mol/g, micro reinforcement as reported in Table 2.

The basic formulation for the rubber Samples in this and following Examples is presented in the following Table 1.

Table 1

Material	Sample
First Non-Productive Mixing (NP-1)
Natural cis 1,4-polyisoprene rubber¹	80
Emulsion SBR rubber²	20 (with 7.5 phr oil)
Carbon black³	41
Free (additional) rubber processing oil⁴	2.5
Zinc oxide	3
Antidegradant⁵	1
Polyoctenamer (Micro, Example III)⁶	variable; 0-20
Ultra High MW Polyethylene (Micro, Ex I)⁷	variable; 0-20
Cellulose (Macro, Example II)⁸	variable; 0-12
Polyaramid pulp (Macro, Example III)⁹	variable; 0-4

Productive mixing (PR)
Sulfur	3
Accelerators (curing aids)¹⁰	1.5

¹Natural cis 1,4-polyisoprene rubber (SMR -20)
²Copolymer of butadiene and styrene rubber as Plioflex™ 1778 from the Goodyear Tire & Rubber Company
³Rubber reinforcing carbon black as N299, an ASTM designation
⁴Rubber processing oil
⁵Quinoline type
⁶Polyoctenamer as Vestenamer 8012 from the Degussa Company
⁷Ultra high molecular weight polyethylene (UHMWPE) as GUR4120 from the Ticona company having an average molecular weight of about 5,000,000 mol/g.
⁸Cellulose in a form of surface treated fiber as Santoweb D™ from the Flexsys Company.
⁹Polyaramid pulp in a form of a natural rubber masterbatch as GF 722 from the DuPont Company
¹⁰Accelerators as sulfenamide types

The rubber samples were prepared by mixing the elastomers(s) together with reinforcing fillers and other rubber compounding ingredients in a first non-productive mixing stage (NP-1) in an internal rubber mixer for 4 minutes to a temperature of 160°C. The resulting rubber composition is then mixed in a productive mixing stage (PR) in an internal rubber mixer with sulfur curatives for 2 minutes to a temperature of 110°C. The rubber composition is sheeted out and cooled to below 40°C between the non-productive mixing and the productive mixing steps.

The following Table 2 illustrates cure behavior and various physical properties of the rubber samples. Where a cured rubber sample was evaluated, such as for the stress-strain, rebound, hardness, tear strength and abrasion measurements, the rubber sample was cured for 23 minutes at a temperature of 170°C.

Table 2

	Samples
	Control
	A	B	C
Micro reinforcement, HMWPE (phr)	0	10	20
Mooney viscosity, ML(1+4) at 100°C	88	101	100

Rheometer, MDR) ¹ , 160°C, 30 min
Maximum torque (dNm)	18.8	19	18.6
Minimum torque (dNm)	3.1	3.7	3.7
T90 (minutes)	4.4	4.5	4.8

Stress-strain, ATS, ring tensile, 23 min, 170°C ²
Tensile strength (MPa)	18.7	16.5	16
Elongation at break (%)	468	392	366
100% modulus (MPa)	1.7	2.6	3.4
300% modulus (MPa)	10.8	13.1	14.2

Rebound
23°C	54	54	55
100°C	68	68	68

Shore A Hardness
23 °C	62	68	71
100°C	59	65	67

RPA test, 11 Hz, 100°C ³
Uncured G' at 15% strain (MPa)	0.26	0.31	0.33
Modulus G' at 1% strain (MPa)	2.2	2.6	3.0
Modulus G' at 14% strain (MPa)	1.4	1.7	1.9
Tan delta at 10% strain	0.10	0.09	0.10

Green Strength, with grain, at 23 °C⁴
80% stress (MPa)	0.33	0.35	0.43
240% stress (MPa)	0.54	0.40	0.52
480% stress (MPa)	0.58	0.50	0.68
Maximum stress (MPa)	0.68	0.89	0.89
Maximum strain (%)	1012	1210	987

Tear Strength, 95°C, Newtons⁵	84	70	71

¹Data obtained according to Moving Die Rheometer instrument, model MDR-2000 by Alpha Technologies, used for determining cure characteristics of elastomeric materials, such as for example Torque, T90 etc.
²Data obtained according to Automated Testing System instrument by the Instron Corporation which incorporates six tests in one system. Such instrument may determine ultimate tensile, ultimate elongation, moduli, etc.
³Data according to Rubber Process Analyzer as RPA 2000™ instrument by Alpha Technologies, formerly the Flexsys Company and formerly the Monsanto Company
⁴Data according to stress-strain analysis of uncured rubber composition.
⁵Data obtained according to a tear strength (peal adhesion) test to determine interfacial adhesion between two samples of a rubber composition. In particular, such interfacial adhesion is determined by pulling one rubber composition away from the other at a right angle to the untorn test specimen with the two ends of the rubber compositions being pulled apart at a 180° angle to each other using an Instron instrument at 95°C and reported as Newtons force.

From Tables 2 it can be seen that the compound Shore A hardness and stiffness (100% and 300% moduli) of Samples B and C were significantly enhanced, as compared to Control Sample A, from the introduction of ultrahigh molecular weight polyethylene into the compound (rubber composition).
This is considered herein to be significant in a sense that ultrahigh molecular weight polyethylene provided some reinforcement to the rubber compound as a rubber layer of Samples B and C spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
From Tables 2 it can be seen that hysteretic properties (e.g. tan delta at 100°C) of the compound (Samples B and C) were similar to those of Control Sample A and therefore considered herein as not being significantly affected from the addition of ultrahigh molecular weight polyethylene into the compound.
This is considered herein to be significant in a sense that maintaining the hysteretic properties of the rubber composition would substantially maintain the heat build up property (e.g. not significantly increase the heat built up during the running of the tire) of the rubber composition as well as the rolling resistance performance, of a tire containing an rubber layer of Samples B and C spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.

Example II

Rubber samples of rubber compositions which contain a macro reinforcement for use for an abridging rubber layer for the split carcass ply of this invention (to span the gap between the carcass split ply ends) is prepared and identified herein as Control Sample D and experimental Samples E, F and G which contain cellulose macro reinforcement as reported in Table 3.

The basic formulation for the rubber Samples is presented in Table 1 of Example I.

Table 3

	Samples
	Control
	D	E	F	G
Macro reinforcement, cellulose (phr)	0	4	8	12

Stress-strain, ATS, ring tensile, 23 min, 170 °C²
Tensile strength (MPa)	12.3	9.7	11.2	9.3
Elongation at break (%)	414	345	366	304
100% modulus (MPa)	1.5	2.1	2.9	3.7
300 % modulus (MPa)	8.3	9.1	9.8	--

Rebound
23°C	51	51	50	51
100°C	60	61	61	62

Shore A Hardness
23 °C	59	62	65	69
100 °C	56	58	61	66

RPA test, 1 Hz, 100°C ³
Uncured G' at 15% strain (MPa)	0.26	0.27	0.28	0.29
Modulus G' at 1% strain (MPa)	1.7	1.8	1.9	1.9
Modulus G' at 50% strain (MPa)	0.7	0.8	0.8	0.8
Tan delta at 10% strain	0.11	0.11	0.11	0.10

Green Strength, with grain, at 23°C ⁴
80% stress (MPa)	0.36	0.45	0.58	0.86
240%stress (MPa)	0.40	0.57	0.69	0.98
480% stress (MPa)	0.52	0.77	0.88	1.26
Maximum stress (MPa)	1.14	1.39	1.28	1.71
Maximum strain (%)	1140	995	950	918

Tear Strength, 95°C, Newtons⁵	119	110	93	44

The superscript numbers refer to the same measurement methodology used in Example I.
From Tables 3 it can be seen that the compound Shore A hardness and stiffness (100% and 300% moduli) were significantly enhanced from the introduction of cellulose fiber into the compound.
This is considered herein to be significant in a sense that cellulose fiber provided some reinforcement to the rubber compound.
From Tables 3 it can be seen that hysteretic properties (e.g. tan delta at 100°C) of the Samples E, F and G, as compared to Control Sample D, were not significantly affected by the addition of cellulose fiber into the compound.
This is considered herein to be significant in a sense that maintaining the hysteretic properties of the rubber composition would substantially maintain the heat build up property (e.g. not significantly increase the heat built up during the running of the tire) of the rubber composition as well as the rolling resistance performance, of a tire containing an rubber layer of Samples E, F and G spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
From Table 3 it also can be seen that the green strength of the compound was significantly enhanced for Samples E, F and G, as compared to Control Sample D, by the addition of cellulose fiber into the compound.
This is considered herein to be significant in a sense that the increased green strength would improve the tire building process for the green, uncured tire prior to the shaping and curing step for the tire.

Example III

Rubber samples of rubber compositions which contain micro and macro reinforcements for use in the abridging rubber layer for the split carcass ply of this invention (to span the gap between the carcass split ply ends in the crown portion of the tire) is prepared and identified herein as Control Sample H and experimental Samples I and J for polyoctenamaer micro reinforcement and K and L for aramid macro reinforcement as reported in Table 4.

Table 4

	Samples
	Control
	H	I	J	K	L
Micro reinforcement, polyoctenamer (phr)	0	10	20	0	0
Macro reinforcement, aramid (phr)	0	0	0	2	4

Stress-strain, ATS, ring tensile, 23 min, 170°C ²
Tensile strength (MPa)	13.2	9.3	10.2	10.9	11
Elongation at break (%)	415	337	376	319	303
100% modulus (MPa)	1.5	1.5	1.5	3.2	4.4
300 % modulus (MPa)	9	6.6	8.1	11.3	12.2
Rebound
23 °C	52	55	56	51	50
100 °C	62	63	64	63	62

Shore A Hardness
23 °C	56	55	53	65	67
100°C	52	55	57	51	50

RPA test, 1 Hz, 100 °C³
Uncured G' at 15% strain (MPa)	0.26	0.23	0.19	0.32	0.32
Modulus G' at 1% strain (MPa)	1.8	1.5	1.3	2.2	2.2
Modulus G' at 50% strain (MPa)	0.8	0.8	0.7	1.0	1.0
Tan delta at 10% strain	0.11	0.10	0.09	0.10	0.10

Green Strength, with grain, at 23°C⁴
80% stress (MPa)	0.33	0.49	0.65	0.65	1.64
240% stress (MPa)	0.33	0.59	0.74	1.23	2.49
480% stress (MPa)	0.39	0.76	0.95	1.60	2.94
Maximum stress (MPa)	1.02	1.44	1.73	1.91	2.96
Maximum strain (%)	1363	1103	1073	763	587

Tear strength, 95°C, Newtons⁵	111	109	77	136	137

The superscript numbers refer to the same measurement methodology used in Example I.
From Tables 4 it can be seen that the compound Shore A hardness and stiffness (100% and 300% moduli) were significantly enhanced from the introduction of aramid fiber into the compound.
This is considered herein to be significant in a sense that aramid fiber provided some reinforcement to the rubber compound.
From Tables 4 it can be seen that hysteretic properties (e.g. tan delta at 100°C) of Samples I, J, K and L, as compared to Control Sample H, were not significantly affected by the addition of polyoctenamer or aramid fiber into the respective rubber Samples.
This is considered herein to be significant in a sense that maintaining the hysteretic properties of the rubber composition would substantially maintain the heat build up property (e.g. not significantly increase the heat built up during the running of the tire) of the rubber composition as well as the rolling resistance performance, of a tire containing an rubber layer of Samples I, J, K and L spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
From Table 4 it also can be seen that the green strength of the compound was significantly enhanced from the addition of polyoctenamer and aramid fiber into the compound for Samples I, J, K and L, as compared to Control Sample H.
This is considered herein to be significant in a sense that increased green strength would improve the tire building process for the green, uncured tire prior to the shaping and curing step for the tire.

Example IV

Rubber samples of rubber compositions which contain micro and macro reinforcement for use in an abridging rubber layer for the split ply tire carcass of this invention (to span the gap between the carcass split ply ends) is prepared and identified in this Example as Control Sample M (with a combination of natural rubber and emulsion SBR) and Control Sample N (with natural rubber) and experimental Samples O and P (corresponding to Control Samples M and N, respectively) which contain cellulose macro reinforcement as reported in Table 6.

The basic formulation for the rubber samples is presented in the following Table 5.

Table 5

Material	Sample
First Non-Productive Mixing (NP-1)
Natural cis 1,4-polyisoprene rubber¹	100 or 80
Emulsion SBR rubber²	0 or 20 (with 7.5 phr oil)
Carbon black³	41
Free (additional) rubber processing oil⁴	10 or 2.5
Zinc oxide	3
Antidegradant⁵	1
Cellulose⁸	0 or 12

Productive mixing (PR)
Sulfur	3
Accelerators (curing aids)¹⁰	1.5

The superscript numbers refer to the same measurement methodology used in Example I.

Table 6

	Samples
	Control
	M	N	O	P
Natural rubber	80	100	80	100
Emulsion SBR rubber	20	0	20	0
Macro reinforcement cellulose (phr)	0	0	12	12

Rheometer, MDR ¹ , 170°-C, 30 min
Maximum torque (dNm)	17.2	15.6	18.7	17
Minimum torque (dNm)	2.8	2.5	3.1	3
T90 (minutes)	2.4	1.6	2.5	1.7

Stress-strain, ATS, ring tensile, 32 min, 150 °C²
Tensile strength (MPa)	12.5	13.7	8.5	7.9
Elongation at break (%)	405	510	280	312
100% modulus (MPa)	1.5	1.1	3.9	3.1
300 % modulus (MPa)	8.9	6.2		6.9

Rebound
23 °C	50	53	50	52
100°C	64	62	63	61
Shore A Hardness
23°C	61	57	70	66
100°C	54	50	65	60

RPA test, 11 Hz, 100°C³
Uncured modulus at 15% strain (MPa)	0.25	0.24	0.27	0.25
Modulus G' at 1% strain (MPa)	2.9	2.5	3.3	3
Modulus G' at 10% strain (MPa)	1.45	1.20	1.6	1.4
Tan delta at 10% strain	0.10	0.10	0.10	0.11

Green Strength, with grain, at 23°C ⁴
80% stress, (modulus), (MPa)	0.27	0.27	0.57	0.53
240%stress, (modulus), (MPa)	0.29	0.58	0.72	0.71
480% stress, (modulus), (MPa)	0.28		0.76	0.79
Maximum stress (tensile strength, (MPa)	0.61	0.57	0.95	0.97
Maximum strain, (elongation), (%)	2478	455	1307	957

Tear Strength, 95°C, Newtons⁵	78	153	49	107
Cord adhesion, 23°C, Newtons⁶	87	96	115	121
Cord adhesion, 121°C, Newtons⁶	149	165	150	145

⁶Data obtained by measuring force in Newtons for a cord pull-out test of the cords embedded in the cured rubber composition.

The superscript numbers refer to the same measurement methodology used in Example I.
From Table 6 it can be seen that the combination of all-NR and macro cellulose reinforcement for Sample P, as compared to the rubber blend and macro cellulose reinforcement for Sample O, led to a significant enhancement of the tear strength of the compound.
From Table 6 it also can be seen that the 23°C cord adhesion of the Samples O and P, as compared to Control Samples M and N, respectively, was maintained or improved by the incorporation of the macro cellulose fiber into the rubber compound.
This is considered herein to be significant in a sense that the macro cellulose-containing compound can be used in combination with fiber cords for further enhancement of the strength of the rubber layer composed of Samples O and M spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.

Claims

A tire comprising an outer circumferential rubber tread (2) with a supporting underlying carcass (3), wherein said carcass (3) contains at least one circumferential continuous cord reinforced belt ply (8) underlying said rubber tread (2) and at least one split carcass ply underlying said belt ply (8), the at least one split carcass ply comprising a pair of cord reinforced rubber carcass ply elements (4, 5), wherein the split ply ends (4A, 5A) of said split carcass ply elements (4, 5) being spaced apart from each other in a central, crown portion of the tire (1), wherein at least one central rubber layer (7A, 7B) spans the gap (6) between said ply ends (4A, 5A);
wherein:
(A) the central rubber layer (7A, 7B) spans the gap (6) between said split carcass ply ends (4A, 5A) and overlays at least a portion of the radially outer surface of said split carcass ply elements (4, 5), or

(B) the central rubber layer (7A, 7B) spans the gap (6) between said split carcass ply ends (4A, 5A) and underlays at least a portion of the radially inner surface of said split carcass ply elements (4, 5), or

(C) a first and a second central rubber layer (7A, 7B) are provided which both span the gap (6) between said split carcass ply ends (4A, 5A),
wherein:
(1) said first central rubber layer (7A) overlays at least a portion of the radially outer surface of said split carcass ply elements (4, 5), and

(2) said second central rubber layer (7B) underlays at least a portion of the radially inner surface of said split carcass ply elements (4, 5);
wherein the rubber composition of said central rubber layer(s) (7A, 7B) contains a dispersion of:

(3) a reinforcing filler comprising at least one of a rubber reinforcing carbon black and synthetic amorphous precipitated silica, and

(4) at least one of:
(a) a macro reinforcing filler, and

(b) a micro reinforcing filler;
wherein said central rubber layer(s) (7A, 7B):

(5) exclude internal continuous cord reinforcement (9), or

(6) include internal continuous cord reinforcement (9);
wherein said macro reinforcing filler, if used, is composed of short fibers comprising at least one of synthetic and natural fibers; and
wherein said micro reinforcing filler, if used, comprises at least one of particulate syndiotactic polybutadiene having a melting point (MP) in a range of from 170°C to 225 °C and poly alpha-olefins having a melting point (MP) in a range of from 80 °C to 180 °C.
The tire of claim 1 wherein the rubber composition of said central rubber layer(s) (7A, 7B) contains from 30 to 100 phr, alternately from 40 to 70 phr, of at least one of said rubber reinforcing carbon black and precipitated silica.
The tire of claim 1 or 2 wherein the rubber composition of said central rubber layer(s) (7A, 7B) contains, based upon parts by weight per 100 parts by weight rubber (phr), from 2 to 30 phr, alternately from 5 to 20 phr of said at least one of said macro and said micro reinforcing filler comprising:
(A) from zero to 30 phr, alternately 5 to 20 phr, of said macro reinforcing filler, and

(B) from zero to 30 phr, alternately 5 to 20 phr, of said micro reinforcing filler, provided that the total amount of macro and micro reinforcing filler is within said range of from 2 to 30 phr.
The tire of claim 3 wherein the rubber composition of said central rubber layer(s) (7A, 7B) contains, based upon parts by weight per 100 parts by weight rubber (phr), from 2 to 25 phr of said macro and micro reinforcing fillers comprising:
(A) from 1 to 25 phr of said macro reinforcing filler, and

(B) from 1 to 25 phr of said micro reinforcing filler, provided that the total amount of said macro reinforcing filler and said micro reinforcing filler is within said range of 2 to 25 phr.
The tire of at least one of the previous claims wherein said short fibers are in a form of a chopped cord of a plurality of said short fibers.
The tire of at least one of the previous claims wherein the average length of the short fibers of said macro reinforcing filler is in a range of from 1.3 to 25 mm.
The tire of at least one of the previous claims wherein the short fibers for said macro reinforcing filler are selected from at least one of nylon, polyester, rayon, fiberglass, aramid, cellulose and cotton fibers.
The tire of at least one of the previous claims wherein said micro reinforcing filler comprises an ultra high molecular weight polyethylene.
The tire of at least one of the previous claims wherein said poly alpha-olefin comprises at least one of polypropylene, poly 1-butene and poly 4-methyl-1-pentene.
The tire of at least one of the previous claims wherein the rubber composition of said central rubber layer (7A, 7B) comprises at least one of natural cis 1,4-polyisoprene rubber, styrene/butadiene rubber and cis 1,4-polybutadiene rubber.
The tire of at least one of the previous claims wherein said first and second rubber layers (7A, 7B) are in contact with each other to form a unitized configuration within the gap (6) between the split carcass ply ends (4A, 5A).